In obtaining the electrical characteristics of components and packaging structures, such as integrated circuit devices and multilayer ceramic substrates, it is absolute requirement that the connection from the tester to the device or structure under test, have a controlled electrical environment so as not to distort the test signals and test results. This is especially important and demanding in light of the ever increasing circuit speeds and density of the devices under test.
Also increasing, in addition to the circuit speeds of the integrated circuits are the number and density of the interconnection pads on the integrated circuit device and the packaging substrate. Namely, the density of the circuitry on a monolithic device is increasing as the art advances. This increase in circuit density in an integrated circuit, in many, if not all instances, dictates a greater number and density of the connection pads on an integrated circuit. Correspondingly, the number and density of connection pads on packaging substrates must be increased to accommodate the increase in number and density of connection pads of the high circuit density integrated circuit devices. Further, as the circuit density and speed of the integrated circuit increases the conductive paths within the packaging substrate increase in number and density and their length must be reduced or at least not increased. Also, the number and density of the conductive pads on a packaging substrate increase as the number and density of the conductive paths therein increase. These factors oppose from a practical, or fabrication point of view, the ability of a contacting system to achieve a minimum acceptable distortion free environment. These factors, as the art progresses, render the testing of integrated circuit devices, and interconnecting packaging structures more difficult. As the art progresses, the testing problems requiring solution are many and complex. Included in these test problems are electrical environment, namely the electrical contacting of a densely spaced array of pads with each electrical connection having substantially equal and minimum uniform impedance characteristics. In testing, the electrical connections to the pads must be made rapidly and precisely, must not place undue stress on the pads, must not mechanically damage the pads, and the input signals to, and output signals from the device under test must not be subjected to distortion or delay.
A major portion of the electrical path from the tester to the device under test and return is used for the space transformation function. Its purpose is to take a large multiplicity of electrical conductors from the tester which are spaciously arrayed and transform them into a highly dense array, similar to, or identical to, the densely spaced device under test input/output pad pattern or array. Since the conducting path length from the tester to the device under test is dominated by the space transformer, for electrical testing to be done successfully, a constant impedance environment is necessitated. Reference is made to the publication "AC Space Transformer for Multipin Systems", by A. Perlmann et al, in the IBM Technical Disclosure Bulletin, Volume 16, No. 8, January 1974, pages and 2725. In this publication the space transformer disclosed and depicted provides electrical continuity under AC environment between contacts that are positioned on close centerline spaces to a larger array, which enables conventional contact mechanisms to be used. The structures essentially comprises top and bottom plates respectively having the proper array of apertures for accommodating coaxial cables. The coaxial cables each have an outside diameter which gradually decreases toward the lower end housed in the apertures of the bottom plate. A spaciously spaced array of contacts on said upper plate is transformed in space to a densely spaced array of contacts on said lower plate. Each coaxial cable providing a path of substantially constant electrical impedance from a contact on said upper plate to a contact on said lower plate.
Reference is made to the publication "Space Transformer for Use in an Electronic Test System" by R. Bove et al, in the IBM Technical Disclosure Bulletin, Volume 17, No. 3, August 1974, pages 930 and 931. In the publication the space transformer disclosed and depicted employs a plurality of multilayered printed circuit boards. Each board is fabricated to have a single line pattern plane, dielectric planes and a ground plane. The boards are sandwiched together to provide strip-line transmission characteristics, whereby essentially constant electrical impedance is obtained. Additionally, at the center of the spaces transformer, where the signal lines converge, discrete conductive members are respectively connected to each signal line. These conductive members are respectively oriented perpendicular to the signal lines and connected to a planar array of conductive pads on the lower planar surface of the space transformer. The space transformer of the Bove et al publication provides structure for the electrical connection of a large number of discrete conducting paths originating at a tester to the highly dense array of electrical pads of a probe assembly.
Reference is made to U.S. Pat. No. 3,493,858 granted Feb. 3, 1970, for "Inflatable Probe Apparatus for Uniformly Contacting and Testing Microcircuits" to D. G. Baron et al and of common assignee herewith.
U.S. Pat. No. 3,493,858 is directed to an inflatable probe apparatus wherein a flexible bag stretched over a frame has a series of conductors mounted on the frame. The bag is positioned whereby a portion thereof is disposed paralled to the surface of an element which contains one or more microcircuits, the conductors being arranged with projecting probe points extending from the plane of the bag adjacent to the substrate in a pattern coinciding with the pattern of the terminal areas of the circuit on the element. The bag is adapted to be inflated to move the extending probe points into contact with the corresponding terminal areas of the circuitry.
Reference is made to the U.S. Pat. application, Ser. No. 537,514, by Ronald Bove et al, filed Dec. 30, 1974, entitled "High Density Wafer Contacting and System," and of common assignee herewith.
Application Ser. No. 537,514, is directed to a contactor structure employed in a high speed electronic test system for testing the electrical integrity of the conductive paths (or lines) in the packaging substrate prior to the mounting and connection thereto of the high circuit density monolithic devices. The contactor structure includes a plurality of discrete electrical probes geometrically arranged, or oriented to respectively electrically contact a discrete one of said array of conductive pads on said packaging substrate or said semiconductor device. The contactor structure further includes a semiconductor space transformer fabricated by large scale integration techniques and containing a plurality of discrete first integrated circuits. The first integrated circuits of the space transformer being respectively electrically connected to said electrical probes. Second integrated circuitry interconnecting said first integrated circuits is also contained within said semiconductor space transformer. Under control of said test system said second integrated circuitry selectively energizes selected first and second ones of said first integrated circuits. Each of said first integrated circuits contains circuitry, whereby said selected first and second ones of said first circuits will mainfest the electrical integrity of the electrical path therebetween. Namely, the electrical path whose integrity is manifested is the conductive path in the device or substrate under test. The conductive path, or circuit, under test, is the path, or circuit, extending between the pad on said substrate in electrical contact with the probe connected to said selected first one of said first integrated circuits, and the pad on said substrate in electrical contact with the probe connected to said selected second one of said first integrated circuits.
Reference is made to U.S. Pat. No. 3,911,361, granted Oct. 7, 1975 to Ronald Bove et al entitled "Coaxial Array Space Transformer", and of common assignee herewith.
U.S. Pat. No. 3,911,361 is directed to circuit means for connecting a high speed electronic tester to a high circuit density monolithic device under test and where said circuit means includes a unitary structural combination of a space transformer and a probe structure, said space transformer and said probe structure being mechanically and electrically mated to provide a plurality of discrete physical electrical contacts with said device under test, said space transformer including: a printed circuit board having a plurality of discrete electrically conductive contact areas and at least one relatively large contact area; a densely spaced array of discrete electrical contacts; said densely array of discrete electrical contacts being supported by and maintained in space relationship one to another by a material having predetermined dielectric characteristics; a plurality of coaxial cables; each of said coaxial cables having an inner conductor, an outer ground shield and dielectric material maintaining said inner conductor and said outer ground shield in space relationship; each of said inner conductors of said plurality of coaxial cables being connected between a predetermined one of said plurality of discrete electrically conductive contact areas on said printed circuit board and a predetermined one of said densely spaced array of electrical contacts; a plurality of metallic plates for supporting said plurality of coaxial cables in spaced relationship, connection means for electrically connecting in common each of said plurality of metallic plates, each of said outer ground shields of said plurality of coaxial cables, and said relatively large contact area on said printed circuit board; said probe structure having a plurality of electrically discrete buckling beam probes; each of said buckling beam probes making physical and electrical contact with a predetermined one of said densely spaced array of discrete electrical contacts; each of said buckling beam probes having a length many times its cross-sectional area whereby the probes buckle when an axial load is applied thereto.
Reference is made to U.S. Pat. No. 3,731,191 granted May 1, 1973, for a "Micro-Miniature Probe Assembly" to Robert L. Bullard et al and of common assignee herewith. U.S. Pat. No. 3,731,191 is directed to a multi-probe circuit assembly for providing low resistance electrical connections to a semiconductor component of which the electrical parameters are to be provided.
In accordance with the invention disclosed and claimed in U.S. Pat. No. 3,731,191 a contact apparatus is provided in which a plurality of probe elements are fixedly held by a common support housing in a fixed array corresponding with the terminal contact pattern of the circuit device to be engaged for testing. Essentially, the probe elements comprise individual tubular probe guides with individual probe wires, or the like, removably contained and compressible within the probe guides. Fixation of the probe elements in the desired array is provided by an encapsulation housing including a support plate portion of the support housing having a plurality of openings arranged to correspond with the test contact pattern of the circuit device. One end of each of the tubular probe guides is attached to the support plate within the plate openings while the other end is held within the housing preferably adjacent and in abutment with a pressure plate opposite the remote ends of the probe guides. The probe wires are designed such that when fully inserted within the probe guide, they extend a controlled amount beyond the end of the housing support plate while the remote ends of the probe wires abut the pressure plate. The tubular probe guides are high conductivity material while the probe wires are conductive material having high resistance to abrasive wearing. Electrical circuit continuity is made by surface contact of the probe wires within the probe guides which are in turn connected to external connector boards or the like mounted on the housing and having provision for connection to external test circuits or the like.
In U.S. Pat. No. 3,731,191, the probe guides are preferably curved between their ends within the housing. Thus, when contact is made with a test terminal, the probe wires have a spring-like quality and are compressible within the probe guides, the curvature and spring-like qualities of the probe wires causing electrical contact to occur very close to the contact end of the probe guide. Thus, only a short length of relatively high resistance probe wire is in the electrical circuit while the high conductivity probe guide acts as the principal electrical connection with the external circuits. Since the probe guides and probe wires are conductive, the contact apparatus is essentially made of dielectric material, particularly the support plate and the pressure plates. In addition, the probe guides are completely encapsulated within a dielectric material so that the probe elements are mutually electrically insulated as well as being held rigidly in position.
Reference is made to U.S. Pat. No. 3,806,801, granted Apr. 23, 1974, to Ronald Bove, directed to "Probe Contactor Having Buckling Beam Probes," and of common assignee herewith. U.S. Pat. No. 3,806,801, discloses a probe contactor in which each of the probes will exert a substantially constant force on each of the pads on the chip irrespective of the relative height of the pads on the chip as long as the pads on the chip have their height within the predetermined range in which the probes can engage the pads. This is accomplished by forming each of the probes with a length many times its cross sectional area so that each of the probes may be deemed to be a beam. Each of the probes is designed so that it will deflect over a range when a predetermined force is applied at its end engaging the pad to axially load the probe so as to prevent additional forces, beyond the predetermined force, being applied to the pad due to engagement of the pad with the probe.
Reference is made to U.S. Pat. No. 3,806,800 granted Apr. 23, 1974, to R. Bove et al, directed to "Method and Apparatus for Determining the Location of electrically Conductive Members on a Structure", and of common assignee herewith. In U.S. Pat. No. 3,806,800, the electrically conductive pads on a semiconductor chip or the engineering change pads on a multilayer substrate are located electronically relative to probes which are in a predetermined orthogonal orientation, so that the particular probe or probes in engagement with each of the pads is determined. Then, the electrical characteristics of any electrical unit connected to each of the pads is ascertained through selectively controlling the electrical power supplied through the probes to the pads in a controlled manner.
U.S. Pat. No. 3,835,381 granted Sept. 10, 1974, to O. R. Garretson et al., entitled "Probe Card Including A Multiplicity of Probe Contacts and Methods of Making," discloses a probe card useful in testing the effectiveness and utility of semiconductor devices and hybrid circuit substrates prior to the application to such devices and substrates of terminal leads for interconnection with other components. The probe card includes a unitary electrically conductive probe assembly including a multiplicity of closely spaced conductive probes arranged in a radiating array to provide a multiplicity of contact tips adapted to be pressed with uniform pressure and contact resistance on the terminal pads of semiconductor devices and hybrid circuit substances.